Phosphor-Loaded LED Package With Silicone Overlayer for Color Stability

Solution Overview

Problem

Heavily phosphor-loaded LED packages, such as those using the BSY-PFS system, face long-term color and lumen stability issues due to high phosphor loading, leading to color shift and 'trench' formations, especially under humid conditions, limiting their reliability and usefulness in applications requiring stable white light emission.

Innovation Solution

A silicone overlayer is applied on top of the phosphor and silicone blend layer in LED packages to protect the phosphor and prevent color shift, with the overlayer formed by gravitational settling and simultaneous curing to ensure adhesion and prevent separation, enhancing the package's stability and reliability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If high phosphor loading is used to achieve desired color temperature and CRI, then color rendering and color temperature requirements are met, but long-term color stability deteriorates due to color shift and trench formations

Engineering Contradiction:

Improvecolor rendering indexVSAvoidcolor stability

Core Design Contradiction:

Illumination intensityVSReliability

Solution Approach 1:

The patent divides the phosphor layer into two separate layers: a bottom phosphor layer containing PFS phosphor and a top phosphor layer containing BSY phosphor. This segmentation prevents the harmful interactions and trench formations that occur when phosphors are heavily mixed, while still achieving the desired color rendering index and color temperature through the combined emission of both layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a reflective layer as an intermediary between the LED chip and the phosphor layers, and between the phosphor layers themselves. This reflective layer redirects light that would otherwise be absorbed or cause trench formations, improving overall light extraction and color stability while maintaining the desired color rendering characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Temperature

If high phosphor loading is used to meet color requirements, then desired color temperature is achieved, but package stability deteriorates due to trench formations

Engineering Contradiction:

Improvecolor temperatureVSAvoidpackage stability

Core Design Contradiction:

TemperatureVSStability of the object's composition

Solution Approach 1:

The patent divides the phosphor layer into two separate layers: a bottom phosphor layer containing PFS phosphor and a top phosphor layer containing BSY phosphor. This segmentation prevents the harmful interactions and trench formations that occur when phosphors are heavily mixed, while still achieving the desired color rendering index and color temperature through the combined emission of both layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent assigns different phosphor compositions to different spatial locations: PFS phosphor in the bottom layer and BSY phosphor in the top layer. Each layer is optimized for its specific position, with the bottom layer handling certain wavelength conversions and the top layer handling others, preventing the uniform high loading that causes trench formations while maintaining overall color temperature stability.

Inventive Principle:

Principle #3Local quality

3Illumination intensity

If high phosphor loading is used to achieve Hi CRI, then color rendering is improved, but lumen stability deteriorates due to phosphor degradation

Engineering Contradiction:

Improvecolor renderingVSAvoidlumen stability

Core Design Contradiction:

Illumination intensityVSDuration of action of stationary object

Solution Approach 1:

The patent divides the phosphor layer into two separate layers: a bottom phosphor layer containing PFS phosphor and a top phosphor layer containing BSY phosphor. This segmentation prevents the harmful interactions and trench formations that occur when phosphors are heavily mixed, while still achieving the desired color rendering index and color temperature through the combined emission of both layers.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent introduces a reflective layer as an intermediary between the LED chip and the phosphor layers, and between the phosphor layers themselves. This reflective layer redirects light that would otherwise be absorbed or cause trench formations, improving overall light extraction and color stability while maintaining the desired color rendering characteristics.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The silicone overlayer provides a 25-34% improvement in color stability over 500-4000 hours of operation by isolating the phosphor from ambient moisture, reducing color shift and maintaining the desired color temperature, thus enhancing the long-term reliability of the LED package.

Implementation Method 1

The silicone overlayer provides a 25-34% improvement in color stability over 500-4000 hours of operation by isolating the phosphor from ambient moisture

Methodology Applied

Scientific EffectPhysical barrier protection: Physical Containment

Implementation Method 2

The UV curable silicone/phosphor blend is then dispensed onto the LED chip and UV cured to form a stable encapsulating layer

Methodology Applied

Scientific EffectUV curing: Photopolymerisation

Data Source

PatentEP3120394B1Heavily phosphor loaded LED package

Publication Date: 2023.12.20 GE LIGHTING SOLUTIONS LLC

Figure 1~2

AI summary

Heavily phosphor loaded LED packages having higher stability and a method for increasing the stability of heavily phosphor loaded LED packages. A silicone overlayer is provided on the phosphor silicone blend layer.